In recent years, forming of images on various base materials using an inkjet system has been performed. For example, Japanese Patent Application Laid-Open No. 2007-50555 (Document 1) discloses a technique in which, in the case where an image is printed with an inkjet printer on a medium such as a cloth material, a metal plate or leather on which it is difficult to directly stabilize and print an image, an undercoat layer for image fixing is printed on the medium with droplets of ink for undercoat-layer printing that are ejected from an inkjet head, and an image is overprinted on the surface of that undercoat layer with droplets of ink for image printing that are ejected from an inkjet head.
Incidentally, in the case where an undercoat layer for image fixing is formed on a base material (medium) and an image is formed on the undercoat layer with ink for image printing as in the technique of Document 1, ink droplets for undercoat-layer printing are applied to the base material with a 100% dot area rate (in other words, ink droplets are applied to all positions on the base material to which ink droplets can be applied). In this case, however, cockling (a phenomenon in which wrinkles are created) may occur if the base material is paper, or depending on the type of the base material, the ink for image printing may not be fixed appropriately on the undercoat layer, and as a result, the accuracy of an image to be formed on the undercoat layer decreases.